Shock absorber



SHOCK ABsoRBER Filed May 29, 1951 v 4 Sheets-Sheet 1 JNVENTOR. 75 214]] 7254// March 2, 1954 D. T. BALL 2,670,814

SHOCK ABSORBER Filed May 29, 1951 4 Sheets-Sheet 2 IN V EN TOR. .iorrdfff 7,1 547 irfoymel/S March 2, 1954 Filed May 29, 1951 D. T. BALL SHOCK ABSORBER 4 Sheets-Sheet 3 Ei.l4

. INV NTOR. owdf] Zr' 4 Sheets-Sheet 4 2, c 0 2M if MMW. mv/f e 25444 QW .s .e erf/.7a2 i@ my Q Z M ZS. iff/4 Wmv/55%,@ ,m m ,M ,i y 2 n "l: A/IIV D. T. BALL SHOCK ABSORBER March 2, 1954 Filed May 29. 1951 Patented Mar. 2, 1954 SHOCK ABSORBER Donald T. Ball, iOak Park, Mich., assigner to Chrysler Corporation, Highland Park, Mich., a

corporation of Delaware Application May 29, 1951, Serial No. 228,835

1 Claim.

This invention relates to shock absorbers, and more particularly to improvements in hydraulic shock vabsorbers. of the direct acting telescopic type commonly employed to control relative movement between the sprung and unsprung masses of a motor vehicle.

My invention provides improvements inl the functional characteristics and performance of shock absorbers generally similar in a broad sense tothose set forth in the copending application of .Ross E. Lewton and Donald T. Ball, Serial No. 166,958, filed June 8, 1950. However, my present invention ,provides improvements in the structure and functioning of shock absorbers over those set forth in said copending Leviton et al. application.

vIt gis an object of my invention to provide a shock absorber which Will function to provide improved riding comfort relative to ride characteristics of presently known shock absorbers used for example on passenger automobiles, trucks, and buses. In addition, my shock absorber provides a smoother, steadier ride with improved vehicle stability and safety over all types of roads.

Another object is to provide a shock absorber having improved simplicity of construction and assembly such that my shock absorber may be manufactured at relatively lower cost. Furthermore, -my shock absorber has improved durability whereby it will perform eiiiciently in normal serviceover longer periods of use than is experienced withconventional shock absorbers.

Additional objects are to provide a shock absorber employed with improved effectiveness and simplification certain of the teachings disclosed in said copending application of Lewton et al. and to provide a shock absorber having improved characteristics of low `cost manufacture, simplicity 'long life, and ease of assembly.

A further object is to provide a shock absorber of improved damping efliciency and smoothness while at the same time protecting the parts .of the shockv absorber and its mountings in an improved manner against damage incident to severe action tending to produce excessive forces onsuch parts and mountings.

Heretofore it has been customary in commercial shock absorbers of the direct acting type which have been used in the industry for many years to provide damping for the compression and rebound movements by means of orifices with associated pressure -relief valves. Resistance to movement of fluid is induced by relative movements of .the piston `and -cylinder and in such devices the shock absorber `resistance lbuilds, up rap.-

(Cl. 18S-88) idly 4to reach its maximum resistance immediately after the beginning of its stroke as determined by .a conventional blow-off type of pres.- sure relief valve, such maximum resistance remaining approximately constant throughout most .of the stroke Yand then decreasing abruptly just prior to vthe end of the stroke when the reduced piston velocity allows :the blow-off relief valve to again close under the rapidly diminishing pressure ,of ,the fluid subjected to movement of the piston. On .compression strokes a check valve freely permits the pressure of the liquid in the rebound chamber .to equal that in the .compression chamber :so that only that portion of the piston area which is equal tothe rod crosssection is Leffective in producing compression resistance. Such arrangements introduce insuflicient damping control, over the normal range of use, harshness in the ride, and jolting of the passengers.

A typical example of such conventional or prior types of lshock absorbers which is referred to herein in contrast with my shock absorber is shown on pages and 141 .of Chrysler 1940 Shop Manual .(D-863'1), copyright 1940 by Chrysler Corporation, and also on pages *111 and 112 of De Soto 1940 Shop Manual (D-8636), copyright 1940 by Chrysler Corporation.

In addition, with the aforesaid conventional shock absorbers, approximately the same maximum resistance is attained in the shock absorber regardless of the velocity of piston movement for al1 degreesof shock absorber actions Whichopen the blow-ofi valve. Hence the resistance developed by the shock absorber and Athedamping performed is not proportioned or eectively related to the velocity of the piston stroke either on .the compression jounce stroke `or on the rebound stroke. damping forces Vare inefficient and impose undesired limitations on speed, safety, and comfort in vdriving motor vehicles over lvarying types of roads, especially those having Washboard surfaCeachuck-holes, gravel irregularities, or other deviations from the so-.called smooth boulevard surface.

Among other objections to the aforesaid con,- ventional shock .absorbers are diculty in :calibrating the blow-oir valves, noisy action of such valves especially under low temperature .conditions Aexperienced in winter, objectionable lag eiect, rand fan undesirably long period of time in warming-up the oil `in the shock absorber before reaching average normal conditions.

My .invention has among its objectsovercom Such arrangements and methods of f ing the aforesaid undesirable characteristics in conventional shock absorbers, and at the same time improving the structure and functions of the aforesaid Lewton et al. shock absorber. In contrast with prior devices, I employ a novel simplied means for eecting damping with improved efciency and passenger comfort on .both the compression and rebound strokes of the shock absorber.

By reason of my damping control the resistance developed by the shock absorber and the damping performed is proportioned and eiectively related in an improved manner to the piston stroke velocity preferably on both the compression and rebound Strokes. Instead of employing conventional damping action in which under all road conditions the damping resistance rises rapidly to a peak which is then maintained over most of the piston stroke, my damping provides a resistance which builds up smoothly and uniformly in an improved manner to a maximum corresponding generally to maximum piston velocity at substantially the mid-stroke of the piston and then falls off uniformly as the piston reaches the end of its stroke. This pattern of performance for my shock absorber is obtained for varying road conditions and for both of the compression and rebound strokes, the value of maximum resistance developed by the shock absorber being greater as the maximum piston velocity increases and in predetermined proportion to such increases. Thus the performance characteristics of my shock absorber for boulevard types of roads are fundamentally the same as those experienced on roads of varying degrees of roughness, the amount of resistance developed by the shock absorber automatically responding with improved simplicity and eifectiveness to varying piston velocities induced by the forces imposed on compression and rebound strokes and at all times the resistance developed is free from objectionable abrupt variations which result from use of conventional blow-oil valves or other means for bringing about abrupt changes in rate of increase or decrease of pressure of the iiuid in the shock absorber and resulting abrupt changes in resistance.

An object of my invention, in its preferred embodiment, is to provide means of improved simplicity and effectiveness to relieve excessive resistance during relatively high piston velocities during compression strokes of the character which might otherwise have a destructive effect on the parts of the shock absorber and its mounting. With such arrangement as the piston velocity becomes greater, the developed resistance becomes greater. However, such resistance on compression does not increase indirect proportion With increase in piston velocity but rather with progressively lessening increments of resistance increase as the piston velocity increases in equal increments., At low piston velocities this resistance relief is preferably eective for practical purposes but for increasing piston velocities the resistance relief operates at a rate accelerating in its effectiveness as the piston velocities increase.

An additional object of my invention is to improve the eiciency .of direct acting telescopic shock absorbers by maintaining the liquid working chambers filled at all times and thereby insuring against a lag effect commonly experienced in conventional shock absorbers. A lag effect is experienced by relatively free movement of the shock absorber piston prior to its i velocities.

operation on a volume of liquid in a Working chamber and is the result of inadequate supply of the liquid to that chamber during preceding movement of the piston in its opposite direction. In addition to the virtual elimination of lag effect by my invention I furthermore provide improved efciency of shock absorber action by utilizing more of the full area of the piston for action in 4developing resistance on the compression stroke. With my invention the liquid pressure in the rebound chamber is so controlled during compression strokes that the liquid pressure in the compression chamber acts effectively on substantially the full area of the piston, especially at relatively lower range piston velocities, whereby much more resistance is developed on compression than has been possible with conventional shock absorbers of the same size. My invention provides improvements over the aforesaid Lewton et al. application in simplifying and improving the control of resistance relief, when desired, by automatically progressively causing the liquid pressure in the rebound chamber to increase with increases in piston velocities during compression strokes such that in the higher ranges of compression piston velocities the liquid pressure differential across the piston becomes less pronounced as the compression piston velocities increase and consequently less and less of the full piston area is effectively acted on by the liquid pressure in the compression chamber thereby causing a progressively decreasing rate of resistance build-up as the compression piston velocities increase. This automatic control, where desired, accelerates in its effectiveness as compression piston velocities increase over the range of relatively high piston velocities and is of only relatively minor effectiveness or significance in the range of piston velocities between relatively high and low velocities While at low velocities this automatic control is ineffective from a practical standpoint. Such control is highly desirable as it affords maximum efficiency in developing compression resistance over the lower range of piston velocities while automatically lessening compression resistances developed over the higher ranges of piston velocities, the amount of resistance control being readily varied by altering the stiffness of the valve means but without necessarily requiring change either in the size or location of the liquid orifice controls associated with the piston and base check valving.

I have found that my shock absorber operates with such improved damping efliciency that, even though liquid pressures are not excessive, damping forces are developed which, as a practical matter especially in regard to desirability of employing more or less standard size of mounting studs, make it desirable to reduce the damping capacity of the shock absorber on compression in' the ranges of relatively high piston While improved and satisfactory results both functionally and mechanically are obtained without employing my resistance relief feature, I usually prefer to incorporate such feature from the standpoint of minimizing the size of mounting studs for the shock absorber and in providing a shock absorber which can be manufactured with only ordinary attention and consideration to strength and Weight of materials and distortion of parts. My resistance relief feature, when employed, is preferably associated only with the compression stroke as the intensity of rebound strokes is limited largely `trated embodiments of `the principles lof my invention may take the form -of lnotches in the body-of the piston and base valve seat vor in the form of notches in a separate member associated with the piston and base Valving.

In -the aforesaid Lewton et al. application the orifice control between the compression chamber and the reservoir is shown as being provided by a passage of small diameter Vdrilled through a brass plug. My invention avoids the necessity of employing A:brass or other expensive and sometimes scarce materials or of diflicult and expensive drilling of any character whereby this `portion of thecontrol is greatly simpliiied, reduced in cost of manufacture, and functionally improved. In addition, my invention accommodates manufacture under ordinary methods to closer limits so that consistency in performance of quantities of shock absorbers is more readily obtained.

inthe aforesaid Lewton et al. application the control of liquid flow between the chambers above and below the `piston is effected by the formation of small diameter 'passages through the piston. Here again my invention lprovides for greatly lessened cost of manufacture together with improved functioning of liquid flow and overall shock absorber performance. In addition, my invention provides for a substantial lessening, if not elimination from a practical standpoint, of liquidflow noises ofthe type which might disturb an occupant of a'vehicle equipped with shock absorbers, my notch liquid passage means being arranged to direct the .liquid streams toward the walls of the working cylinder at the piston location and toward each other at the ibase valve location. Such arrangement furthermore minimizes harshness which is felt to an undesired degree in prior shock absorbers and avoids high velocityliquid jets impinging toward the check valve. With Ymy invention the check valve has improved freedom of action in insuring complete filling of the compression chamber Vthus avoiding lag effects and increasing the smoothness and general efficiency Vo1? the shock absorber action. this feature contributing 'to eici'ent lilling of the reboundchamber during compression strokes as the rebound chamber starts to ll, without lag, as soon as the piston starts its compression strokes.

,Further objects and advantages of my invention will be Amore apparent fromthe following description thereof which serves to illustrate the principles involved, reference being made to .the accompanying drawings vin which:

Fig. 1 is a sectional elevational viewv through my shockabsorber shown at Vapproximately doug ble scale size.

2 is .a sectional plan view taken along line 2-42 ofFig. 1 across the top of the piston.

Fig. 3 is a sectional plan View of the Ibasevaiv- 6 orifice member associated withthe :piston inv Fig. 21. vFig. i5 la plan view .of the 'notch .escape or orifice lmember :associated .with the `base valvefof Fig. 1. 1

Fig. yt isa view :generally similar to Fig. 1 illustrating :a modification of my invention, the Fig. 6 parts being employed in 'the Fig. f1 .shock :aibsorber in place of the V'corresponding parts 'in Fig. 1..

iFigiZ is a sectional plan view taken along lineV 'l-i 3'of Fig. 6 across the top of .fthe piston.

Fig.. B vis a `sectional plan view taken along line 8-"8 of liign at .the top of the base valve seat.

Fig. l9 is fan .enlarged vsectional relevationalvicw through :one of the piston notches of Fi-g. f6.

'-Fig. 'lo .is an .enlarged sectional elevational view through one `of the 'base vnotches `of Fig. 6.

Fig. .1li is a -sectional elevational view -ofaa'piston assembly rof modified construction adapted foruse my shock absorber assembliesi-n 'lieu of the 'piston assembly ofFig. 1 or Fig. 6.

Fig. '12 -is a similar `view of a furthermodiiied piston assembly adapted for use in'my shock fabsorber l.assemblies in llieu of the piston assembly of Figi or Fig. 6.

- Fig. 13 is a diagrammatic graphical 'illustration of typical performance characteristics lo'f my shock absorber related to vperformance o'f the aforesaid conventional shock absorbers.

Fig. 1'4is .a diagrammatic graphical illustration of performance .characteristics of my shook absorber both lwith and Without the resistance relief valving, ymaximum vfluid pressures 'in lthe compressionand rebound chambers beingplotted against cycles per Vminute of shock absorber operation or Ymaximum piston velocity at such cycles. Y

Fig. 15 is a diagrammatic. graphical illustra-V tion of lcompression resistance kvperformance y-ef my shock absorber.

VIn the drawings 'the shock absorber 1C -of LFigures `1 through 5 and the shock absorber C 'of Figuresf vthrough '10 may be lused to 4advantage with any type of `wheel `suspension and, yin the broader aspects of fthe invention with other mechanisms and ldevices wherein damping of relatively movable bodies isvdesired. 'In applying the improved shock absorber to motor vehicles, it is only necessary to connect operablythe opposite ends of the telescopic-assembly respectively tortwo parts of the vehicle, one part moving in response to rise and fall of the ground wheel, and the other part moving in response `to rise and fall of the body or frame such that relative movement between the parts is under damping control by the shock absorber. A typical ap plication of my shock absorber is illustrated `vin the aforesaid Lewton et al. application for Aloo-th a front and rear wheel suspension o'f a motor vehicle. My shock absorber C or C' is so `con-v structed and proportioned as -to vprovide lwhat may be termed generally optimum results, it being apparent that deviations therefrom may -be undertaken as may `be desired Without departing from the principles of my invention as set forth herein and as definedv in the appended claims. As a typical representa-tion of these prin# ciples I have'shown a front shock absorber which could veffectively and 'to -advantage replace the front shock absorber shown in said Lewton et al. application. y

`With reference particularly `toiigures 1-5 -of the-drawings, the'shock absorber() comprises an assemblyof tubularpartsbaving operatingiloops' 7. or eyes and I6 at its opposite ends. The eye |5 is mounted to the one relatively movable vehicle part |1 which may be a stud, a rubber bushing |8 being disposed between the eye and the stud. 'I'he eye i6 is similarly mounted to the other relatively movable vehicle part |9 which may be a stud, a rubber bushing 2| being disposed between the eye and the stud. Shock absorber C comprises upper body member 26 having an axial bore 21 through which the working piston rod 28 is slidably tted, the latter mounting the eye |5 at its .upper end. Adjacent this eye the rod 28 is shouldered to receive the centrally apertured stamped end cover 29, the eye, rod, and cover being structurally united by a weld 30. Depending from the body in spaced relation with rod 28, is a tubular working cylinder 3| having its upper end press-tting the shouldered cylindrical portion 32 of body 26. The body 26 has a spherical portion 33 iitting within the spherical cap member 34 welded to the upper end of the outer tubular cylinder 35 which is radially spaced from cylinder 3| to provide a reservoir D for the working liquid of the shock absorber. Any of the Well known commercial or other suitable shock absorber fluids may be used as the working liquid in the instant shock absorber.

The end cap member 34 is centrally apertured slidably to receive rod 23 with clearance and forms a secure assembly of tubes 32, 35 with the body 25. Escape of iiuid is prevented by the oilresistant flexible seal ring 35 seated within cap member 34 and fitting around rod 28, a compression coil spring 31 urging the seal ring into contact with the rod and cap member to prevent escape of liquid outwardly between the rod and cap, as more particularly described and claimed in the copending application of Fred Glassford, Serial No. 139,218, iled January 18, 1950. A tubular dirt shield 38 depends from the end cover 29 spaced outwardly from cylinder 35 tc guard against mud and dirt being thrown against the upper end parts of the shock absorber, particularly the rod 28 and parts bounding the space between cover 29 and cap member 34. Any liquid passing upwardly between rod 28 and bore 21 is trapped beneath seal 35 and returns to reservoir D by the grooved passage 39 in the outer face of portion 33.

At the opposite or bottom end of the shock absorber, the cylinder 35 has its end portion tightly fitted around the upper end portion of the bottom cap member 40 and welded thereto at 4| to maintain a structurally unitary fluid-tight fit. The eye |6 is connected by weld 42 with the outer bottom closed face of the cap member 4D. This cap, defining an interior chamber 1i, has three relatively spaced regions of inward deformation as at 43 providing three relatively unrestricted passages for liquid within the cap member between the regions 43 as at 44. The cap member at regions 43 is formed to present a downwardly and inwardly sloping wall to seat a similarly faced annular flange 45 of an annular base valve carrier 45 which is stepped annularly at 41 to pilot and seat the bottom end portion of cylinder 3|. It will be apparent that with the parts assembled as thus far described at the top and bottom of the shock absorber, the parts at the upper and lower end regions of the shock absorber will be maintained in assembled relation as shown.

The inner end of the main or primary portion of the piston rod 28 is reduced at 48 to receive a working piston E which is secured to the piston 8 shoulder 49 thus formed by a fastener 50 threaded on the rod end 48. According to one embodiment of my invent-ion laminated valve means of a novel form composed of a plurality of spring steel discs are clamped in position betweenshoulder 49 and` the upper face of piston E. In the illustrated embodiment of Figures 1-5, this valve means, generally designated at V, comprises three thin spring steel disk or washer annulus members 5|, 52, and 24, each having an opening for receiving rod portion 48. In the illustrated shockA absorber the valve members 5| and 52 provide or control compression resistance relief and for the illustrated shock absorber were made .010 of an inch thick and the member 24 was made .0045 of an inch thick. The upper face of the piston E is provided with an upwardly open annular groove 53 of relatively large capacity for free or unrestricted liquid now around the groove. This groove is spaced laterally outwardly of the rod portion 48 to provide a land 54 on which the inner annular portion of member 24 is seated, the outer annular portion of this valve member overlying groove 53 and seating on the outer piston land 22. The periphery of element 24 is notched by a plurality of notches 23, four in number, spaced circumferentially relative to one another and in the illustrated form were made .125 or one-eighth of an inch in width. A substantial or major portion of the radial length of each notch 23- overlies groove 53 so that the liquid oriiice defined by each notch is the cross-sectional area of the notch above the piston land 22 such area being the product of the thickness of disk 24 times the width of the notch 23. The total area of the orice thus formed is, of course, the sum of the areas of the notches employed in any instance. The rod shoulder 49 overlies a substantial portion of the groove providing support for members 24, 5|, and 52 leaving only the portions of these members which extend laterally beyond shoulder 49 for flexing, as will presently become more apparent. Each of these annulus disk members 24, 5|, and 52 is thus clamped or fixed at its inner pe-, ripheral portion to the piston leaving its outer' peripheral portion free to flex away from the face of the piston bounding the rebound chamber F. While these valve members may, if desired, be subjected to pre-load when assembled, it is preferred for uniformity under manufacturing conditions to clamp these members in position such that member 24 is located flush with land 54, flexing of this member being resisted owing to its spring-like character but primarily by the resistance to flexing provided by the valve members 5| and 52. The four peripheral notches 23 on valve member 24 overlie the land 22 such that the periphery of member 24 covering groove 53 is interrupted at intervals. Extending through the' piston head 55 and preferably on axes parallel to the piston axis for convenience of manuac-` ture, is a'single set of relatively large capacity cored liquid conducting passages 51 shown to be six in number equally spaced around the piston head for unrestricted free fluid now therethrough, these passages opening upwardly to the groove ,53 and downwardly to the space below the piston. It is to be observed at this point that the notches 23 in member 24 provide restricted liquid communication between opposite ends or" the piston E. The radial penetration of each notch 23 toward the center of element 24 is suicient that the minimum thickness of the resulting orifices is measured by the distance from the top ofthe land to the valve element 5|, that is, by the rela- 9 tivey thickness' of element 24. Thus the orice formed at each notch 23 is. defined by the; piston land 22 member 5l, and notch 23..

The piston E has aY sliding fit within cylinder 3| and serves to divide the working space within this cylinder into two chambers bounded by the opposite sides or working-'faces of the piston. The chamber F above the piston, with the shock absorber arranged as shown, is the rebound chamber and is deiined by the volume bounded by the inner Walls of cylinder 3|,l the inner surface cf cylinder closure body 26 and the upper face of piston E or such partsl as are exposed to the fluid. The chamber F is, of course, deiined by its. net. cross sectional area which is the cross sectional area of the interior of cylinder 3i less the cross sectional area of pistonrod 28 and the chan-ge in volume of chamber F, as piston E moves, is numerically equal to the product of this net cross sectional area of chamber F times the distance through which the piston moves.

The other of the two chambers defined by piston E comprises the iounce or compression chamber G deined by the volume bounded by the under portions of piston E, cylinder 3l, and the upperr surfaces of the chamber bounding valve carrier 4.6 and valve parts carried thereby, and more particularly hereinafter described. The; chamberG is, of course, defined by its cross sectional. area which is the cross sectional area of theV interior of cylinder 3l and the change in Volume of chamber G, as piston E moves, is numerically equal to the product of this cross sectionaly area of chamber G times the distance through which the piston moves.`

In the particular shock absorber illustrated in Figurev 1 the diameter of the piston rod 28- is approximately one-half inch and that of the bore of cylinderv IH, and hence the approximate diameterof piston E is substantially one inch. These dimensions are, of course,l arbitrarily selected and are set forth, merely by way of example for the size and capacity of the illustrated shock absorber when employed in the usual type of motor vehicle suspensions; These particular Whole number dimensions are also of assistance for convenience of reference and discussion in illustrating the principles of the instant invention. For example, the ratio of cross sectional areas of chambers G and F is approximately-4:3 and as piston E moves, the chambers G and F vary in volume. in this; same ratio for a given piston movement.

As thus far described, it will be apparent in the improved shock absorber that ony compression or jounce occasioned by a vehicle road Wheel striking a bump in the road, the shock' absorber eyes Il and E6 will movev relatively toward eachother and thel load spring of the suspension (not shown).l will be deflected and loadedin addition to its. static load'. On rebound, as when the wheel recovers'from its jounce movement and when a Wheel fails away from the level into a hollow in the road owing to its own weight and that of its associated parts along with the force of its associ'ated' suspension spring, the eyes t5, and l-G will move relatively away from each other. Moving with the eye l are. the. piston rod 28 and parts attached thereto including piston E,k cover 29, and shield 3d. The remaining parts move with the eyev t6. For convenience of; reference in the specification and claims, the relative movement referred to will, be in terms of relative movement ci piston E, it beings apparent that. the shock absorber action occasioned; by relative movement between cylinder 3| and piston E may be re.- garded as though cylinder 3i were Xed and all movement took place at. eye l5 and piston E.

With the, instant shock absorber providing rapid damping of oscillations with improved efficiency and better comfort to the vehicle passengers, it is not necessary or desirable to provide for quick build-up to a peak resistance maintained through most of the piston stroke in either of the compression or the rebound strokes as is. common practice with conventional shock absorbers. Conventional shock absorbers rely on damping action over a relatively large number of oscillations or cycles between the. sprung and unsprung masses attended by and, in factY in large measure caused by, an insuiiicient amount of work done by the shock absorber foreach of its strokes. Conventional shock absorbers operate with this undesirable. characteristic because, among other things, the resistance mus-t be. kept fairly low to prevent undue harshness for low velocity piston short strokes with the result that there is inadequate resistance providedl'for high velocity piston long strokes. Even with modern compromises ther resistance in conventional shock absorbers. is too great for short strokes and insufficient for long strokes and harshness and jolting is experienced for almost all ranges of operations. Furthermore, conventional shock absorbers do not damp oscillations quickly enough so that on rough roads amplitudes build up unduly thereby limiting vehicle safe. driving speeds and failing to provide the desired degree of passenger comfort.

In contrast with conventional shock absorbers, the instantl improvement overco es the aforesaid disadvantages and undesirable characteristictics. The improved shock absorber operates by utilizing control passages for restricted ow of liquids, such passagesv being of a cross sectional area and number proportionate such that. within the range of piston velocities experienced in automotive practicethe resistance developed'by the shock absorber varies proportionately with piston velocity as may be desired, the resistance being free from undesired abrupt changes throughout the piston stroke, and the pressures developed in the compression chamber G and rebound chamber F being increased and utilized in an improved manner in providing added resistance relative to pressure and resistance relationship in conventional shock absorbers.

In carrying out the objects of the present. invention, there is provided a simple and effective form of liquid now restricting shuttle passage means for restricted flow of fluid back and forth therethrough between chambers F and G when the piston moves in each direction of its reciprocatory stroke. Such shuttle passage means maintains these chambers in communication with each other so that the liquid now resistance characteristic inherent by reason of the size, shape, and number of passages constituting such passage means provides the total resistance to fluid flow through such passage means when considered apart from the enlarging of this passage means by compression relief valving when employed according to certain of my embodiments. The fluid is thus shuttled back and forth through ther open ends of the shuttle passage means in passing from one side of the piston E to the other side.v

Apart from the outlet and. inlet from and to chamber F provided by the" shuttle passage means, the chamberF is otherwise closed during rebound, and Where compression resistance relief is used such resistance is relieved by the valve means V during compression for certain piston velocities. However, because of the differential in volume change in chambers F and G occasioned by piston rod 28 disposed in chamber F, provision is made to accomodate escape of liquid displaced by rod 28 into reservoir D during the compression stroke and to accomodate unrestricted return of such liquid in an improved manner from the reservoir to chamber G on the rebound stroke to insure against cavitation developing in chamber G.

In the present embodiment of the invention, the shuttle passage means, conveniently designated H, is comprised by the notches 23 in the velocity. The lower ends of the passages 51 are,

of course, freely open at all times to chamber G. Chamber G is provided with restrictive liquid escape means for controlling liquid escape from this chamber into the reservoir D. rIhis escape means, according to the present illustrative embodiment of the invention, comprises a jounce or compression chamber liquid escape passage means illustrated in the form of notch escape passage means J between the chamber G and the reservoir D, the latter being freely open through passages 44 and the large diameter unrestricted passage 61 formed centrally through the body 4B. The escape passage means J is shown in Figs. l and 5 in the form of notches 14 and 16 somewhat similar to the notches 23 previously discussed. Notch 16 in the illustrative embodiment shown in Figures 1-5 is of the same Width as slots 23, namely, one-eighth of an inch, Whereas notch 14 is one-sixteenth of an inch in width as such might be termed a half notch, as it were, since it is only half as wide as the notch 1B. These notches are formed in a disc element 12 in the periphery thereof, which element 12 has a central boss-receiving opening 18. Element 12 is received on and is, in eiect, a part of a plate check valve S3 by press t, staking, or other suitable connection. This valve 63 is lightly yieldingly urged by a spider spring 65 toward an upstanding shouldered sea-t 66 bounding the unrestricted passage 61 formed in valve body 46 and concentrically arranged therewith. Spring 65 is secured in body 46 by peenng the annular edge 68 of body portion 41 so as to overlie the annular margin of spring 65, the spring having spring fingers 65 engaging the upper face of valve 63 adjacent an upper boss 69 provided centrally thereon. An opposite boss 19 is formed on the lower side of valve 63 to provide an annularly stepped portion 1U on which is received in fixed relation therewith the notched element 12. This member or element 12 overlies the upstanding valve land 66, the notches 14 and 16 being adjacent thereto with the result that element 12 is annularly dicontinuous about the edges of land 66. The depth of radial penetration of notches 14 and 16 is suiiicient so as to be spaced at their inner edge from land 66 an amount sufficient to insure that the minimum thickness of the notch passage defining the liquid restricting orifice is measured by the thickness of element 12. In the illustrated embodiment 12 shown in Figures 1-5, the element 12 has a thickness of .0045 of an inch.

The escape passage means J has its entrance end defined by the notch and half notch 1B and 14, respectively, and has its discharge end adjacent the top of passage 61 for directly a liquid into the reservoir chamber D disposed between body 45 and the end member 43, the liquid streams being directed into passage 61 thence downwardly into the chamber 1| which communicates freely with the main annular reservoir D by passages 44. A spiral bale member 13 is disposed in reservoir D to prevent liquid in the reservoir D from unduly surging and frothing or commingling with the air above the level of the liquid in the reservoir.

During the compression stroke of piston E when the latter moves toward valve carrier 45, valve B3 will remain seated and prevent any escape of liquid from chamber G to passage 61 except for that liquid which is compelled to flow through the escape passage means J to reservoir D. Liquid flow will take place upwardly to chamber F through the shuttle passage means H and Where the resistance relief valving V employed a small amount of the liquid which will otherwise flow through the shuttle passage means H will, at certain piston velocities, be diverted to iiow between disk 24 and valve seat 22 when liquid pressure in chamber G is sufficient to flex the group of disks 5|, 52, and 24. However, rebound upward movement of piston E has a suction effect on check valve B3 and as this valve is only lightly held to its seat it readily unseats along with the element 12 and freely admits liquid from reservoir D to chamber G so as to maintain chamber G iilled With liquid during rebound after which valve 63 again is caused to seat by spring 65 and by its own Weight.

The shuttle passage means H is so proportioned in respect to the length, number, and cross-sectional area of the notches as to provide the desired damping in predetermined relationship with the liquid escape means J which is likewise proportioned to obtain the desired damping eifect. When theseV parts are proportioned in relationship with one another according to the instant invention, improved damping control is obtained for both long and short stroke rebounds and compressions over the range of piston velocities dealt with in normal use of the stock absorber. Furthermore, the rebound chamber F will be lled at all times and free of objectionable cavitation which would undesirably alter the desired resistances on rebound and produce jolts, noise, and frothing of the liquid.

In contrast with the aforesaid conventional type of shock absorbers, the present device has its liquid control parts so proportioned and arranged as to take advantage of what is called a full displacement principle during compression and particularly during the first part of the compression stroke where lag and resistance build-up is particularly troublesome. During operation of the vehicle the bouncing action at the shock absorber tends to emulsify the working liquid by entraining air bubbles in the liquid with the result that there is a tendency to lose shock absorber action, commonly called fading In conventional shock absorbers resistance Work is not eifected on compression until the piston rod displaces suiicient liquid to rst take up any voids in the compression and rebound chambers and then force liquid through the conventional base valve control. In my shock absorber vthe compression area being. balanced outs vliquid escape means J bears a cooperating relaaumen rinititalmovement or the piston on its compresi- YVsinny strokes quickly transfers any voids in the .compression chamber.l to the rebound chamber Utilization of the liquid? pressure inthe compression: chamber acting. o-n substantially the full. areav of the piston in developing; resistance on compression is:y known as the full displace` -ment principle.

The eiliciency oi. the full displacement rnincipleA increases in proportion to approach to atmospheric pressure on the low pressure side of the piston. This action is;v in contrast with more conventional: arrangements lwherein liquid pressures in the: rebound chamber. are equalized' With liquid pressures inv the chamber during compression strokes', it being apparent that i-n suchg types of shock absorbers the effective-y area of the piston 'in developing shock absorber' resistance is only 'that area equal tothe cross-sectional: area of the pistony rod, the pressure on the remaining kpiston The capacity ot the tionship toV that of the shuttle passage means yH in obtaining this full displacement principle and in determining the: impro-ved' functioning characteristics of my sh'oclr absorber..

In the present shock absorber this relation- -ship is such that lprogressively smooth resista-nce is built up on compression. and rebound strokes While maintaining the rebound chamber F lled at al1- times so as to avoid cavitation.. inasmuch `as the effects of fade are more' noticeable in front shock absorbers than in rear: shockabsorbers and? since the front shock'. absorbers are conventionally called on to perform more Work per inch oi stroke than the rear shock absorbers and alsobecause of other factors including desirability to provide rebound' resistance. in the vfront shock absorbers in an amount as high as practicable in closely approaching the amount of compression resistance provided by the front shock absorbers, the present shock absorber of Figures lis illustrative ofV a front shock ab* sorber and represents approximately the optimum efficiency in developing both rebound and compression resistances.

Such optimum characteristics contain as one desirable factor the predetermined relationship between the total area of the shuttle passage means H and that of. the liquid escape means J as related to the volumes ofv liquid displaced on rebound and compression. Such relationship for thel samey given stroke on compression and rebound` may be expressed in the following terms for the illustrated arrangement of shock. absorber parts:

A1 is the total area of the shuttle passage 'means H effective during rebound;

A2 is the total area of the liquid escape means J A3' is the cross-sectional area of the chamber F which is for all practical purposes. equal tothe 'cross-sectional area of the piston E less the crosssectional. area of piston rod 28; and

A# is the cross-sectional area` or piston rock 28.

14 Employing suchtermsf then Ar Az EFA-i Inmy shock' absorber, this ratio: for the. given l" cylinder and 1/2 rod for optimum results approximates 3 to 1 preferably alongl with the sizes of the shuttle passage means I-Iv and the esca-pe means- J rela-tively proportioned; according to my teachings. Y y

In striving to generally preserve this ratio, my. resulting shock absorber will provide'frebound resistance approximating resista-nce oncompression to the fullest extent which'v be; realized for a given size shock absorber. Deviations in the relationship of from approximate equality with Aa E is such that as A1 ZE.

increases above equality, lossesv in rebound refsistance will be effected' at a greater rate than losses in compression resistance but the shock absorber Will still operate with less and less developed resistances for a given size device. Oni' minor deviation of' Alv E from approximate equality with in. the direction of lessening. the value of A1 E mayv be. tolerated' as deviation. in this. direction tends: toward cavitation primarily in. the cham-,.

ber F along with all resulting evils including noise, harshness, aeration, lag, and generall inefciencies. Along with this desirable relationship is the further relationship, fromI practical standpoints, that the total area of the shuttle passage means shall be about, and at least not greatly less than, .4% of the cross-sectional area of. the chamber F as more particularly herein,- after set. forth. yThese optimum relationships are such. as to provide rebound resistances most closely approximating compression resistances, good: performance at lower range piston velocities', avoidance of excessive liquid. pressures,y use of liquids of unusually low viscosity, and leakages, and avoidancey of requirements to main.- tairL undesiredv accuracy in limits of the various oriice sizes.. f

Because of. the longer Wheel travel per inch oi shock absorber piston movement in the usual vehicle installation forr the front shock absorbers as' compared withr the relatively lesser Wheel travel per inch of piston movement for the: rear shock absorbers, as set forth in saidr Leviton et al. application, it is desirable to provide somewhat higher resistance by the iront shock absorbers than for'l the rear shock absorbers. Furthermore, in many types f suspension, static. fric.- tion, load, wheelbase, andv spring rates may, by 'Way of example,l lbe very4 different at the front ami the rear ofythe vehicle with the result that it is desirable to proportion the damping effect of the front and rear shock absorbers to compensate for such differences. Thus to adapt the illustrated shock absorber to a rear shock absorber type it may be desired to increase the sizes of the passages H and J or to provide increased resistance relief, as by providing weaker springing at valving means V.

It is to be pointed out that during compression the shuttle passage means H through piston E between chambers G and F is responsible for most of the resistance work or damping developed by the present shock absorber, the liquid escape means J being responsible for a lesser amount. In the example chosen for illustrative purposes wherein the areas of the piston E and the rod 28 are in the ratio of 4:1, the shuttle passage means H is responsible for up to as much as approximately 75% of the total compression resistance work because it handles substantially three times as much iiuid as passage means J which, of course, must pass the iiuid displaced by rod 28 into the reservoir chamber D. By electing such relatively great amounts of resistance Work in the shuttle means H which is confined within cylinder 3|, the iiuid is much more rapidly heated in the Working chambers F and G and the shock absorber reaches its average normal working temperature condition much more rapidly than with conventional shock absorbers. By the instant method of damping there is effected more energy absorption at a given fluid pressure than heretofore, most of the energy absorption being effected through the shuttle passage means which is self-contained within cylinder 3|. The escape means J is so proportioned in relation to the shuttle passage means H that the escape flow means J will provide a rate of discharge into reservoir D at any pressure developed in the compression chamber G under varying piston velocities such that at any given piston velocity the escape means J will pass slightly less fluid in proportion to the displacement of the piston rod area alone than all the fluid being handled which is passed from below the piston to above it in proportion to the displacement of the piston area less the rod area, the excess insuring against cavitation in the rebound chamber F.

As will be apparent from Figure l, the chamber F is closed except for the communication of the open ends of the passages 51 with the notches 23. Any liquid which may work past rod 28 will drain from the collecting chamber containing spring 31 down through passage 39 in member 2S and into reservoir D. Chamber G, except for the check valve 63 which is unseated during rebound, is closed to reservoir D except for the communication alorded through the unrestricted central opening 61 and the notch and half notch 16, 14 in disc 12. On rebound, check valve 63 freely admits fluid from reservoir D to chamber G in quantity replacing that ejected through passage means J on compression. The point is to be here emphasized that the valve means V of Figure l is not a blow-off valve but is rather a resistance control or resistance relief valve. That is, this valve means does not relieve fluid pressure in the compression chamber but it does function to relieve resistance which would otherwise develop on compression especially in the range of high piston velocities. The passage means H and J are so proportioned relative to each other and with respect to the liquid displacements deiined by the cylinder 3|, piston E, and rod 28, that the rebound chamber F will be maintained i'illed during compression strokes irrespective of any opening of valve means V or seepage of liquid past this valvemeans.

Consequently, the opening of the valve means V in the slight amounts occurring in operation does not result in passing any more fluid, in practical measurable quantity, from chamber G to chamber F than would take place Without the valve means V opening. Chamber F is maintained iilled on compression stroke without valve means V opening at all, and obviously additional fluid of a practically incompressible nature cannot .be admitted to an already full chamber. However, fluid is diverted from flow through the shuttle passage means H to the increasing area afforded by the valve means V when relatively opened at the higher piston velocities which bring about a reduction in the existing pressure differential across the piston, and it is apparent that at the higher piston velocities a small amount of liquid will flow past valve means V during compression but such ow as may take place due to the movement of valve means V is very small. The displacement of the piston E is so large in proportion to minutely small quantities of liquid necessary to raise the pressure in chamber F during compression strokes, particularly at the higher piston velocities, that, as aforesaid, the additional amount of liquid passed due to movement of valve means V over and above what the notches 23 would pass without movement of the valve means V at a given piston velocity on compression is small but suicient to alter the pressure differential across the piston. The effect of flexing of the valve means V is to increase the capacity of the shuttle passage means H under conditions of relatively high piston velocity. If desired, the physical characteristics of valve means V may be altered to increase this capacity over that illustrated herein in order to lessen compression resistance.

In the modiiication of Figures 6 through 10, the shock absorber C', in similar fashion to shock absorber C of the iirst embodiment, comprises a combination of parts including a dirt shield |38, an outer tubular cylinder |35, tubular working cylinder |3l, piston rod |28, piston E having a piston head |55, spiral baille member |13, cap member |40, spring biased check valve |53, and a base valve carrier |46. The parts of the shock absorber C to the extent to which they have been thus far described, are simi-lar in proportion, number, arrangement, and size, to the corresponding parts of the lirst shown embodiment, and cooperate to produce a liquid-containing rebound chamber F', compression chamber G', reservoir D', central passage |61, and interior chamber |11, three passages |44, and a plurality of passages |51 corded in the piston head |55.

The liquid-containing chambers and passages just named are like the corresponding chambers and passages in the first embodiment as to volume, shape, number, and size, besides functioning in the same capacity. On the other hand, in the modied embodiment shovvn'in Figures 6 through l0, the shock absorber C has a shuttle passage means H' and escape passage means J formed respectively in the iixed valve elements of the piston E' and base valve |46; that is to say, formed in the valve seats. Such formation is described particularly as follows.

Piston E of Figures 6, 7, and 9 has its upper face provided with an upwardly, open annular groove |53 surrounded on the outside by a raised d. .circumferentially 1i notbesl, .1111s- 3l tratedas'threein Y' be 'shaped'as de- ..Siredl VHoiivever',j.to exs' .anuia'ctufeit is. desiredt'o formthenetches' y ja' coining y,operation so that thendtchesare preferablyV-fslped Or ofthe-.travez 'd @ses 1.."11 shownfinifie- 1:ure Sasjthis :ape15eeSi1Y'fvtmtdthmueh a -v suitable coiningoperation upon [the top oipiston .head lvfotpisltonE P ton Elhasalaminated resistance-"relief .valve ans VC. comprised by Ytwo thin. .spring Steelmlsher va1t di$1 f.mmbersg i 5I and |52. yInthevnlustrated.embodiment effiggures .6, '7, and9,thelvalvenienibers.,|51 an'dJSL-i are made-.OlOpf al {rich-1t ick nld;clamped bey 'tween'.pistonheadilSnandsh 'ered' rodl` 28 so as to oyerlie'rland. |221 and` .n'o .tche V['23t 'Hencethe peripheral seating- ;"sur:fac'ev`` of 'the p l valve 5* means isinsef'ectjmotehedf Wh ejthevalve members. l5.' @edit-25ms besubieted to mislead-whenassembled. it still preferable y thesame as with the first `embodinient forhuni- .formitrunder meeefeilirinacedties t0 Clamp `thegvalve, members in p tion'suchthatmember 115| is locatedqiiushbut vn stressed initsrelation to land |2212I fiexi v ofthisgvalve member. being resisted Aowing` t it* Loring-l'ikecharaeterk` and to assistance `from th I newse` unpreloaded--va1v memberyl52-.g- Lp eiedgenotchesyj in land i122 areloyerlainwby valv A embers'llland l5 lhefserin .Eigures .5, .8

:,Cirgumferen .all ,Se

. n .numbers meer he'trapegoidaljcross 'eure i10..a`n`d are sectionmartl arly .....easilyeformedbya :.,z'the seattace fof Xe valA result Qipiiov .ethebeseavalve boss. ;l 9 .fOr-meri ne naproare vstr-aight-sided-andg,eachqggieiines a passage Awinch,nmthe:inaspettati sheehabserber-ofzlench .piston and einchgroehima satisactfllybe'ofv a topv widtngidimensionf 0f3's0f157tf-eh0tt0m dth fdi-men'sion ofe..035!., anddepthffrom; top tozb ,K tom yof .020. .p For.prnpeesrelativefpnoportiqningfwith .wz .the .dimensions just .enumeratedand indineawith preserving.; within;theeoptirnunniassignedlimits .-\.-.theratiosof top to bottom of --.020. j. ample just given the ratio of areas bottom width dimensionof .0155` and depthV from In the` illustratedy eX- numerically .effected is approximately 3:1, .where 'Althetotal areaof the shuttle passage means Hifand A2 is'the' total area of liquid escapemeans JSeiective during the. jounce compression stroke,

ally notation being .similar tothatusedin the dis- -cussion of the rst embodiment. AOther andvarious satisfactory notch combinations will be read.-

iiy suggested-in the .light of my vteachings 4and within the-broader aspects of the invention.

IIn the modied 'pistonarrangement of Fig. 11, I have illustrated the same notched disk 24 of Fig. 11 associated Awith the same piston .How- ..ever, instead of this disk 24 operating as a valving element andv instead of this disk being yieldingly seated by overlying disks 5I, 52 as in Fig. 1,

the notched disk 2li of Fig. 11 maintains its posi- 4tion seated on land 22 and hence has no function of resistance relief on compression strokes.

@To this end the disk 24 is heldconstantly xed .with the piston in any suitable manner asA by l clamping it in position by a stiff unyielding steel l washer disk 98e of vappropriate thickness such as Y M3 to insure against appreciable yielding action under liquid pressuresv developed in chamber G. Notehes 23 are preferably as shown and described in connection with the Fig. 1 embodiment.v .This

' Fig. 11 piston isfadapted to be substituted for the piston in-the Fig. l assembly or inthe Fig. 6

- assembly.

In Fig. l2 I have shown the notched piston E of Fig. 6 fitted with the rigid disk i8@ of Fig. 11. l Thus Fig. 12 is very similar to Fig. 11 and funcequivalent to' each other in that the liquid escape from chamber F is limited to the. shuttlepassage means of-notch form.

Y From what has been said herein foreach of the illustrative Vembodiments of the principles of my invention it will be apparent that the shuttle passage Vmeans H or H hasa predetermined capacity to conduct or flow liquid-.under` pressuretherethrough. This-liquid ow capacity will, of course,

,vary as the liquid pressure differential .between chambers F and G varies Yand is determined by l the size, shape, and number of the passages which constitute the shuttle passage means as. aforesaid. When this has been determined according to the teachings of my invention, apart from considerations 'of compression relief valvingl where employed, the liquid iiow capacity. of the'shuttle passagemeans will thereby be xed or constant 'l 'for 'anygiven liquid pressure differential and. Will thereby determine the liquid new resisting .charv vacteristic of theshuttle passage means in effectl' ing resistance to Ymovement ofthe shockfabsorber piston-lover itsV rang'eiof velocities -incident to apredeterrnined capacity to conduct or iiowsl'iquid therethrough-when subjected to a liquid. pressure --diii'ferentialfbetweerr chamber G orG.'. ar'id^ the reservoir D or D and this liquid flow capacity will likewise vary as the pressure differential varies. The liquid flow capacity of the liquid escape means is likewise determined as aforesaid by the size, shape, and number of the passages which constitute the escape passage means and when this has been determined, according to the teachings of my invention, the liquid flow capacity of the escape passage means will thereby be xed or constant for any given liquid pressure diiierential and Will thereby determine the liquid flow characteristic of the escape passage means in effecting resistance to movement of the shock absorber piston in the direction of its reciprocatory movement toward the check valve means 63 and over its range of velocities incident to normal use of the shock absorber.

Because of the inherent characteristic of the shuttle passage means to restrict flow of liquid between chambers F and G for example, the shuttle passage means H may be said to restrict free flow or escape of liquid therethrough between chambers F and G when piston E reciprocates. This is in sharp contrast with the aforementioned conventional shock absorbers having a pressure relief or check valve associated with one or more conventional liquid conducting passages Which are of such large liquid flow capacity as to permit or accommodate free how of liquid therethrough so that when the valve is open the liquid in the conventional rebound chamber is deliberately permitted to substantially equalize its pressure with the pressure of the liquid in the conventional compression chamber when the piston stroke is toward the conventional check valve controllingly associated with the liquid reservoir.

In Figs. l, 6, 1l, and l2 the notch form of the shuttle passage means H or H' provides substantial improvements over the arrangement in said Lewton et al. application. rangement lends itself to improve ease of manufacture, lower cost, and improved performance. It is customary as a matter of practical expediency to permit manufacturing tolerances in the dimensions of the various parts of the shock absorber including the orifice portions, such permissible tolerances necessarily entering into the proportionate and dimensional relationships expressed as desirable herein so as to render these values only approximately accurate. However, with my invention the desired relationships may be more nearly obtained as it is a simple matter to obtain a good degree of accuracy in coining or stamping the notches of the various liquid flow restricting passages. The coined notches of Figs. 6 and 12 provide further simpliiication and ccst reduction in that these notches at |23 and V55 are formed in parts E, E', d6, and |116 which are already present in shock absorbers thus minimizing the number of parts required.

An additional feature of my invention over said Lewton et al. application resides in more consistent and better performance of shock absorbers especially when turned out in regular quantity production, including quieter operation and more uniform filling of the working liquid chambers and operation of the piston without lag. In my arrangements incorporating notch orices it will be noted that during compression strokes the liquid jets or streams are directed by the notch shuttle passage means H or I-I' substantially radially of the piston and cylinder axis toward the inner walls of the cylinder 3| or |3| rather than parallel to such axis. In addition, during compression, the liquid streams are di- My notch arsoA rected through the escape means J or J inwardly of passage El toward the axis of the cylinder and passage and Where multiple notches are employed, as illustrated, these streams impinge on each other within the passage "il and reservoir chamber or Such arrangements have been found to substantially reduce noise eiects incident to liquid flow during operation of the shock absorber on compression strokes. Furthermore on rebound it will be noted that the fluid streams from the notch shuttle passage means H or H are directed inwardly toward the axis of the piston rod portion 48 and not parallel thereto toward the base check valve 63 or |63. This allows the check valve to have an improved freedom of lift movement in response to suction in chamber G or G unhampered by the liquid jets in passing liquid from chamber F or F to chamber G or G. This action permits the effective use of a light check valve spring 65 and insures more positive rell of chamber G and G' during rebound strokes as these chambers start to ll immediately during the rebound strokes and are not required to catch up on the refill as such strokes continue. This in turn insures against lag when the piston next starts its compression stroke after rebound, and reduces or eliminates tendency to harshness, bumps, and noises as the piston reciprocates.

Where compression relief valving is employed, as in my Figs. l and 6 embodiments, I prefer to employ multiple spring steel disks, as at 5|, 52, or |5|, |52, rather than a single disk although any number of spring valve disks may be employed as long as the total spring action is such that the desired valving relief is obtained. Mem ber 24 may be thicker than noted herein in which event notches 23 will be proportioned to preserve the total area as noted herein for the same size shock absorber and the strength of the coacting spring disk or disks made proportionately less as the thicker disk 24 will then provide substantial spring resistance action. It is noted that stresses incident to springing of the compression relief disks is desirably minimized in any one disk by using a plurality of spring disks. The notched disk 24 of Fig. 1 is relatively ineffective as far as relief valving action is concerned as, in the illustrated embodiment, this disk is only .0045 of an inch thick Whereas disks 5|, 52, |5I, |52 are .010 of an inch thick. The stilness of such disks varies, generally speaking, as the cube of the thickness of the disk which largely nullies the effect of disk 24 functioning as a relief control in comparison with this function of the disks 5|, 52, or |5|, |52 although disk 24 does of course have some degree of functioning for relief con trol. If desired a single disk of appropriate greater thickness for the same general performance may be substituted for the two disks 5|, 52, or |5|, |52 or more than two disks of thinner dimension may be employed.

My shuttle passage means H or H' and the escape means J or J are of substantial length in contrast with sharp edge orifices which in general provide ow resistance proportionate to the square of liquid velocity. In general sharp edge or very thin disk orifices are not as desirable as my notch arrangements, for example, as they tend to build up resistance too fast. With my arrangements I provide adequate resistance control at low piston velocities without undesired overcontrol or excessive resistances at high piston velocities and I consider the arrangements of Figs. 11 and 12 Without compression resistance ef fines or encompasses in following my teachings""for'"mostTeiiicientm 301'Si-alpximatelyF298to 1.v

` results.

1"; Shen be-eppr'exiretely fequm to i'sn'iuch as for- Ithe illustrated 1 Y shoclieabsorber-fhying 1'1 cylinder diameter and 1/ ---piston-rod diameter is A3v to 1,

Another way of expressingithefdesired relationship ofthe totalia'iealoflthesiirttlevpassagemeans I in terms off lsnoekifabsminerss offrvasrying Ivsizes, it

' oloed onf compressionefndff'allt ytnfithefresistance-1 on xalfcorisiderationiof strength mponentffpartsofithefshock ngspfsei'ctionf offlspe'cial iquds'- t vvanrdf against brakingrfdownlof @the 4; orkir'gf lquidgndmore careful consideration of A manufacturingtolerances? v"Usuallyitris found to from: equality `With bei-more desilralbl WHer-e additional resistance is I A3 desi'dioveithat provided' bylmyi-illustratedshfock E; absorbers,` to 'increasfltiie 'size 'flthismmt rather for optimum results and as aforesaid wlarger tionship may beexpressedewththe desireddegree desired. Everything considered thedesiredrela-V 23 maximum velocity-at approximately mid-stroke on compression and rebound.

It is, of course, a, diflicult matter to speak with deniteness on shock absorber performance under conditions of boulevard ride, small bumps, medium and big bumps encountered by the vehicle. A small or medium bump in the roadway can become a big bump at higher vehicle speeds and a Big bump at high speed can be a small bump at low vehicle speed. I have resolved this difficulty by translating such variables into terms of piston velocities since this is a definite yardstick of operating conditions and determines the functioning of the shock absorber under all conditions. With this in mind piston strokes which produce maximum piston velocities up to say the general neighborhoodof around .6 ft. per second may be considered as low range performance, around 1.3 ft. per second average or medium range performance, and around 2.6 ft. per second high range or rough road performance, it being understood that velocities considerably in excess of 2.6 ft. per second are Often experienced on compression and may go even as high as around 6 ft. per second. However, I have found that a shock absorber which performs satisfactorily at the piston velocities noted Will usually provide good general performance on the road and therefore these iingers will be fairly representative for purposes herein of referring to low, medium, and high rangeshock absorber performance.

I desire to further point out that it is extremely difficult to accurately measure liquid pressures in chambers F and G at the point of maximum piston velocity over the ranges of performance. However, I have obtained data which is believed to be fairly accurate and at least representative of a pattern of performance unique to my shock absorber although closely related to said Lewton et al. application. l

Referring to Fig. 13, I have somewhat diagrammatically illustrated certain typical performances of my shock absorber and my novel damping principles in contrast with typical conventional performance characteristics referred to hereinbefore.

In Fig. 13, I have illustrated typical rebound resistance curves |85, |86, and |81 developed by machine operation of my shock absorber, resistance being plotted against piston travel, the machine being of the Well known type employed in shock absorber tests in which the piston is moved relative to its cylinder with approximately simple harmonic motion derived by connecting a rotating crank with the shock absorber piston rod. 'I'hese curves |85, |86, `and |81 illustrate forced resistances developed by my shock absorber during operation of the test machine for a 3" typical stroke for 55, 100, and 200 R.V P. M. or cycles per minute respectively and substantially duplicate actual performance of the shock absorber on the vehicle for variations in conditions between mild and severe compressions and rebounds. In each instance, the resistance builds up smoothly under fluid damping to a maximum at approximately piston mid-stroke regardless of maximum piston velocities indicated at |88 and then falls off smoothly under fluid damping to zero as the piston reaches the end of its rebound stroke. It will be noted that the resistance build-up portion of each curve up to the piston mid-stroke at |88 is similar to the remaining half of the curve when the resistance diminishes from the piston midstroke to the end of the stroke. The rebound curves |85, |85, and |88 are also typical of performance of my shock absorber with or without valve means V or V as affect rebound performance.

The compression resistance curves companion to and completing the cycle of rebound curves |85, |85, and |81 are shown in Fig. 13 at |89, |90, and |5| for my shock absorber of my Figs. 11 and 12 types Without valving means V or V while the companion curves for my Figs. 1 and 6 shock absorbers with valving means V or V are shown at |89, |92, and |93. It will be observed that there is no appreciable difference in compression resistance at 55 cycles per minute with either the Figs. 11 and l2 or the Figs. 1 and 6 arrangements and, in fact, very little difference at cycles per minute but as the cycles per minute increase, with proportionate increase in piston velocity, the compression resistance falls oif at an accelerated rate relative to increases in compression resistance for the Figs. 1 and 6 arrangements. It will be noted that with my Figs. l and 6 arrangements the compression curves |89, |92, and |93 are substantially similar to the rebound curves |85, |86, |81 and is made possible by the valve means V or V which so controls compression resistances, especially in the range of maximum piston velocity at |88 Where peak resistances are developed, as to limit these resistances in comparison with their valueswith the Figs. 11 and 12 arrangements according to curves |89, |98, and |9|.

I have obtained good results with my Figs. l1 and 12 arrangements but I have found that resistances developed on compression, especially for extreme Wheel jounce movements produce resistances which cause failure in mounting studs which are conventionally employed. Although these studs and parts mounting them can, of course, be made of such size and strength to prevent failure, I nevertheless prefer in most types of passenger car installations to reduce these peak resistances and my Figs. 1 and 6 arrangements accomplish this control. Before describing the functions of valve means V or V in further detail I will, by Way of contrast, refer to more conventional blow-off valves of conventional shock absorbers.

In Fig. 13 I have illustrated typical performance rebound curves |94, |65, |96 and compression curves |91, |98, |98 for a conventional shock absorber referred to herein as being of the blowof type in which uid pressure in both the iounce and rebound chambers builds up rapidly, then abruptly flattens off with only slight buildup for nearly all of the piston stroke, and then abruptly falls off. These curves illustrate the same conditions of operation and furthe same size shock absorber as for my Fig. 13 characteristics, the scale being the same. Thus the Fig. 13 conventional characteristic curves could be superimposed for comparative marked contrast but for clarity they are shown adjacent each other where comparison may be conveniently made.

In Fig. 13 for each of the Widely varying piston velocities as determined by the test machine crank operation at 55, 100, and 200 R. P. M. corresponding to rebound resistance curves |94, |95, and |56, respectively, and compression resistance curves |91, |88, and |99, respectively, it will be apparent that the curves are very close to each other and that peak resistances developed are nearly the same in spite of the Wide variation in piston velocity. Thus in each instance resistance rapidly builds up over the very short initial portion of the piston stroke 200 at which this valve means does not 4 time .thesonrentional.bliiwbffrelisisralsespells.' toprevent. further substantialriressure rise.- This. l. results4` in .an abrupt .-objectionaLchange, inthe s rateof .resistanceincreasd .the resistancefateblovk. offabeing. generally,.maintained Lthroughnearly the Y entire .piston ,.stroke... as indicatedg by -the stroke Tportion ..201 .g .The slight-,resistance riseto the mid-point, 20.2...duringthefstxgoke' portions 2&1... is largely.. the result .of slight'.\ added.. resistance.,A toruid ow- .through` the .blokw-.offyalye- Tli'en `10 as:1 the piston velocityggapproacheserest Y,ati .the endl-of` .fits fstroke. with .resultingfdirninuti n ,of fluid-,pressure on ...thepistonf .the blow-.oli .Valve closesaabruptly. andsth'e..resistance rapillylralls. off '-tofzero during thesmallfportion.ofthe termi-t` .15 nal .1f-piston .stroke .-as... at .2 0 The ,compression characteristics- -.l 91,- I 98,.. and .,199 fforthis con-w. ventional type of shock absorber are substantially., thefsameas the rebound-curves e194, I..s5,par1.dfl. 96.

Returningnow .tothe .valve...means. Y or.. V of- 20 Figs. 1 and6,1this.valv e,:is nota blow-oft. v alven. and it -is nota pressure relie f.valvefs 11ch.-ashaye i. heretoforev xbeenacommon. :in .priorv` v .shock .ah-f... sor-bers. 4.The .performancecurves..1.9L!.to |.99.of. Fig. 13 illustratev theffunctioning of..convell.t.ona1,..25 shock absorbers on- .both compression Aan c i..,re boundwherein.pressure-.in-.both thescompr sion.. andffthe `rebound -;chambers,.is prevented. from risi-ngq,v substantially f above-. a predetermined.-` amount virtually regardlesssoffincrease.inpistonV velocity;thecOnVentiGnal ,Valuing functioning :toA relievje-pressures-in'eachhamben vin excess of. suchgamount. In'c ontrasi-WithYsuch,conventional pe,trahir-mance;v my yalve means does not .-apprec'r-f ablyrelieve anys-huid-v pressure .in .thefcompression 35 chamber Ialthough it *does` function to` relieve ref. sistanse'whichfsvould'.-Qherwiseodeyelop:on corri:LA pression especially inthe frangepfsrelatiyely..high.. piston\ -yelociti es. Y

Myfflatpspring. steel-.'dislrsl 5 l-,...52,. for.l 51,A 152%() constituting walvingymeans-N or V functions tol.. progressivelyfincreaseithe rpressure .in... .chamber F, oncompression; :such pressure .increase in Figs. l andi incompar-ison .With-VmytFiglrll .Vor;l2'ar.. rangement; Abei-ng` negligible for relatively.. lows@ piston velocities but building. ,up atfan accelera.. ated. ratefas-pistonvelocitiesincrease.overthe rel-, ath/ely; `high --range of piston; velocities., Where ree i. duction; of peak resistance ,forcesis desirable With y. each of the; embodiments of .shock-l absorbers -;substantially the'fullpiston area is ef-W fective ftof develop; compression resistance. (up. to aroundj or. 55 cycles perY minute ,offshock abe... sorber opera-tion. yInfotherWords,=ir1.,this. range of operatontheuidpressure in thecompression., ch amber,- *on -compression--acts against the., .-full piston area in developingcompression resistance. AsV the; cycles increase with lcorrespendirig increase in. .maximum pistonfvelocity, Valve. means-,N in Fig. l, -wzvh-icl'iis typicalfof the Qperationof. valira@ meansffV' -'of lFigfi,#functions .totprogressivelyl al?. low pressure .to -.build;.up Vinnthe rel'iound.chamber, F duringfcompression strokes, Withyeryflittlegrate ofrgbuil up rat-1 irst but :rapidly acceleratingr in. rate; of I build upr as .pistonvelocities .appIDach 200. cyclesfoI-eoperationfand. above.-. When.press1 1re inythe ,-reboundfchamber increases., A aboue. atmosf. pheric .during compressionstrokes,V onlyithedif-v: ference; in pressure in chambers G rand@ ,is eff. feCt'Ve-ron the areaeof the-pistonlessfgthatmfthe pistons-0d; thema-apparentthat .-thegrrsssfllfsln chamber@ G'is furthermereaaluaysseiety ine.-

derelopinacomoressieri-resistenceby; ctms areaiofethcpistomequalita that ofthevrodoza-.soa

thatibyabuildins upstherpressureiniihee #75 26.-.L chamberthe.total..resistanepn.compression be controlledand diminishedlbyvalve mean A Therefore, While theyalvemeansfjl 'doesgno atV any time equalizev thepressurel in elchalmber Gf and F it does trend in `this .direction.:especlallyl i When the compression strokesbecome ,extre f During ,compression strokes oftheshoc A sorber the. resistance developedis determi by the differential of pressures in chambers and G. AThus the compression resstanceyis thefpres?V sure of. theliquid .in .the compression chambe G times the cross-sectional areafof thepisto E less .the pressure of .the liquid. in l:the .'rebo` chamber. timesY that. ,portion Aofthe Apiston a that- .bounds this chamber, i. .e.,the .cross-se, tional area .of .thelpiston less thatof itherod When. the pressureA of. the liquidv inthe rebound chamberis atatmospheric Athen the. resista` is the .product of the compression.chamber Y sure-times the..piston.area..., As vthegpressu p .I the .sliquidin the rebound chambervincreasesfit will lbe. .apparent ,that the l,.re sistance, .ebasedr on L' the Naforesaid .pressure differentialrjwilljb than the product of the compressicnhcham i Ipressure times the piston area but at anytirri thecompression strokethere willbesomejpor orper cent ofthe full `pistonarea which, hen multiplied by. the compression chamber pre ur will equal the resistance. developed. atsuclfiT ti and for convenience of reference suchspo t1 or per cent is designated as the feiectivefpls area. For. example, when the pressureofgt liquid in the reboundchamber. is atwatmosphl i then the full piston area is effectively. bythe pressure of the liquid-,in .the comp vss chamber. in producingcornpression resi 'anc If the .liquid pressureswere substa in v.chambers F and G as .is.,custornaryjinjfcon ventional shoclvabsorbers actingbncompress n@ thenthe.effectivepistonareaWouldbe i v i tion which is equalftothqcrossfsectional are rod .28.. and the.compressiongesstan would e... equal l to .theprodutofthisarea times heap'r sure ofthe liquidpin"thecompressipn/cham rV Thus, Vforany given liquid pressllrefmjc1 X pressionhamben the. .effective `ivistor.;.ar a...fo1;`

comnressiohresistance Will desreasefromft pis-tomarse as..,pressure oftheliquid inpth .re l bound chamber ir1. 1feises.7 mmyshb '.I hayerrovded animproved ...construction jr liquid 110W. Qontrol on compression stroke.. by, as, piston. velocities increase i toward Whishgwoilldi result Vin undesirably..hieh Vcom pression.- reSiStanCeS.,. suchhresstahce's. are 'kept ,j within. desirable .limits by. utilizinethe com ret 'sion ychamber pressures. to v.increase .the d reb chamber pressuresthus diminishing the,portions` of .th'e,piston areawhich are effectivelynacted o bythe pressure of., the Vliquid .in the compY W: Chamber. .theV rate .of Such increase .beine @091er ated asthepistonj ivelocities .approach theiriinax mum] .values ...under :Conditions ...Beemster d whatever-user@ which. the Shockfabsrhert-isputa Therefore, .while referencesherein to the ,effective piston area. relationship Iwith compression. cham benpressure. offers. a convenient .manne1;,of,ex pressing .compression resistance..characteristicsoi myshock. absorber, this rel ationship.fiseactualh'. buts.` a .computed j equivalent, foriponifenie reference. .of-.-.the-m0re.11v01rsdfdifferential sure expressed .above in terms ofy liquid pressa in the f compression, charnbe r-Crsaiid` n,`r th r boundchamberlli" along..iwithjtheirsrespectiy relatedtcrossfsectional.areas;of..h,.piste... 5

For a typical 3" stroke of my shock absorber on the test machine, operation at 50 cycles per minute provides a maximum piston velocity of .65 foot per second, 55 cycles providing a velocity of .715, such operations corresponding generally to ordinary conditions of vehicle travel over fairly good roads and arbitrarily designated as the low range of operation of the shock absorber. Operation on the machine in the medium range at 100 cycles per minute produces 1.315 maximum piston velocity and corresponds approximately to vehicle travel over average moderately rough roads and at the high range of' 200 cycles, producing 2.63 maximum piston velocity, there is fair equivalency to what may be termed very rough roads. Under extreme conditions a piston velocity as high as around 6 feet per second has been experienced. These equivalencies are only general as opinions vary as to classication of degrees of road roughness but will nevertheless serve to generally correlate the functional data given herein for my shock absorber with vehicle ridecharacteristics and to demonstrate the value of machine test data.

The function of my valve means V or V asa resistance relief valve by controlling the amount of piston area effective in developing compression resistance as distinct from conventional pressure relief valving is an important characteristic of the Figs. 1 and 6 shock absorbers. In Fig. 14, for example, I have shown approximate performance of the Figs. 1 and 6 as well as the Figs. 11 and 12 shock absorbers operating at a 3". stroke, maximum fluid pressure in pounds per square inch being plotted against cycles per minute and the equivalent maximum piston velocity in feet per second. In Fig. 14 curve 205 shows generally the maximum pressure in the compression chamber G both Without the valve means as for Figs. 11, 12, and with the valve means V,.or V as for Figs. 1 and 6, the valve means having no appreciable eifect as aforesaid on fluid pressures developed in chamber G. It is apparent that pressures developed rise at an increasing rate, especially after around 100 cycles per minute and in fact pressures in chamber G have been measured as high as 5000 p. s. i. for extreme piston velocities.

With the Fig. 11 or 12 shock absorber the maximum pressure in the rebound chamber F during compression strokes increases above atmospheric pressure moderately after around 50 or 55 cycles, as ,noted from curve 266, becoming somewhat more pronounced in the rate of increase as the piston maximum velocity increases. However, while substantially the entire piston area is effectively acted on by the fluid pressure in chamberG during compression strokes up to around 50 to 55 cycles per minute, much of the full displacement principle is eifective even at 200 cycles whereunder the conditions noted substantially more of the piston area is similarly eifectively acted on than the area equal to the piston rod.

Throughout practically all of the normal range of activity on the vehicle, all illustrated embodiments ofY my shock absorber utilize an effective portion of the piston acted on by the iluid pressure in chamber G during compression strokes which eifective area is more nearly equal to the full cross-sectional piston area than to the crosssectional area of the piston rod. This is apparent from Fig. 14, curve indicating the effect of the compression reliefvalve means in reducing the eiective piston area on compression by building up the iluid pressure inthe rebound chamber at a small rate of increase over the Figs.

11 and 12 performance between around 50 to 55 cycles and 100 cycles and at an accelerated rate of increase thereafter. In each instance, either with the Figs. 1 and 6 or Figs. 11 and 12 arrangements, the Whole effect of the full displacement principle is available throughout the entire compression stroke of the shock absorber up to around 50 or 55 cycles per minute, this being of substantial advantage to avoid fading which is a noticeable characteristic of conventional shock absorbers. Furthermore, the whole eiect of full displacement principle is effective during the initial compression stroke over the whole range of performance of the shock absorber, the values indicated by way of example at 20G and 201 in Fig. 14 being maximum pressures attained in the rebound chamber at the instant of maximum piston velocity. Y

I desireY to again point out that the values shown in Fig. 14 areapproximate owing to extreme difficulty in obtainlng accurate data 4for theV illustrated pressures under conditions of shock absorber operation. However, they illustrate approximate conditions and general pressure trends which I have measured.

Referring to Fig. 15, I vhave illustrated the characteristics of my shock absorber as hereinbefore described. For convenience of'reference the shock absorber which is equipped with my resistance relief valve means V or V' of Fig. 1 or 6 is referred to as havingA relief orV relief valve means and the other embodiments in Figs. 11 and 12 as not having this reliefor relief valve means. In Fig. 15 I have shown compression resistance in hundreds of pounds plotted against cycles in R. P. M. of 3f' stroke machine operation and the equivalent maximum piston velocity incident to such operation as in Fig. 14. Included also is a table showing approximately the per cent reduction in total compression resistance effected by the provision of my relief valve means at various piston velocities.

Performance curve 2118` indicates the compression resistance of my shock absorber Without relief valve means as for example in Fig. 11 and Fig. 12 or in the other figures if the eifect of the relief valve meansis nottaken into consideration. At 2139 I have shownthe resistance developed by my shock absorber, in al1 illustrated forms, by the flow restricting` effect of the liquid escape means J or J alone. In other words the curve 209 represents compression resistance by the action of piston nrodY displacement alone just as though the piston was removed. Curve ZIS represents the compression resistance developed by my shock absorber of VthetypeV having my relief valve means as in Fig. 16116.

It is to be noted that curves 240 and QcS'are merged together for piston` velocities below approximately .8 foot per second or just about at the Ylow range upper limitof around .6'5 to .'73 foot per second which corresponds to the maximum piston velocity on the test machine operating at 50 to 55 R.. P. NI. "Therefore Whether or not the relief valve means 'is incorporated in the shock absorber the louT range compression performance characteristic is substantially identical showing that the shuttle passage means is effective to the same extent in the low range. From the table in Fig. 15 it will'be noted that around the Ymedium or intermediate range which has been arbitrarily selected at around 100 R.`P. M. or 1.315 feet per` second pistonwelocity the' relief 'valve' means,

Y whenpresent, has now eiectd amarked separa- Vtion'between curves'll'a axidZl'lL 'the table indiawesome zweef-therme sh k1 sseiibefzresistaneeiseff-lof@ means in 'l 'auf off-my@illustratedFembouimemsffofr-15 per'sed piston -velocity the'f table' shows* that the valveineans' has eifected'only; '4 `reduction 1 in thconprss'ionresistance.' fTne reduction in 'Y compression 1""resistance eiectedf" by i' the fvalve means'then"Yibecomsomuchtimore? "=pronoun'c'ed, ^f35 being- 26.7% 'fat fthe" assumed: intermediaterange i velocityof `l315"feet'persecond:Y The-upperflim'it 'i of the high range,"assu-med*to be' `about-l.S17-fiest per"seco`rid'fpstoh velocity, is -vattended by'about 40.5% inresistancereduction byfthe valvevrneans; this reduction increasing througlrthehigh-range By substitutingfrweakeriivalve" olisks'fi'or those shown" at f 5 i 52 f' or I 5 I 5L'` or "by increasing vthe f 'f total 'area` of "theshttle passa-'ge means 'H r'orHi f and Vthe` liqudfescapefmeans f5 or r'J'-pr byeffectfefi ing-'alli of th'esechangesy thefresistancef'develonede by the 'shock absorber Lrnayfbe flessened ft'c any deffsired"e'xtentand;ofl our'se;tl1efeciency will also" be 'cori-espndingly'reduced:-

If desirediany'-fof myf disclosed shuttle passage-,- means'mayfwithinfthe broader aspectsofwmyin ventionjoe employed' With'either-form off'frnyfes" capey meansv J or 2l for'any of shuttle ,passage-r means-may "be 'usedfvvith other forms ones/cape. means such astnatedisclosedfin said-Lewt'on-.etal application or mor'fconv'entional ibasef-valvefcon= r structions. Likewise my escape means J or J may be used "toadva'ntage with other forms of shuttle passage means such as disclosed in said tional types'offliquid"controls between'i the rebound and compression chambers.

In each" of the illustrated embodiments of my inviition thereis Yprovided' an"` unrestrictedll'iql uidpassageway means""const1tuted"by thepiston"` c5` passages '51 A'and' "annular" groo v`e"63"" for 'openingvv` the chamber G forfreeliquidotf'tothe erigagei' seat portions `provideci"iesp ctively`` at therpist'on" land 22and the adjacentdislrfof the disk 'means' chamberrF isrgen'erall'y speakingapproximately"f at *atmospheric "pressure f'folrlow'l'llrange* piston velocities?bothfwitli and wit-hout; relief yalving; less thanf-arounvdi foot per secondiy such-'pressure in Lall-n`stan'ces increasing proportionatelyto increases in maximum velocityof'the' piston4 during compression strokes and more rapidlyfeinfcreasingwith tlieFigsl and 6 valvingV "or V.

In-the foiegoindescriptinrof mycompressionl f relief ljlfalvingmea-nsrV T1andi VlI haveset forth for^i11ustratiye--purposes"a typicalf xampleof the Y principlesfinvolved in"the'flcontr'olpfcompression resistanceiwhereinf this valviime'ans is 4ineffective 1 to relieve*- 'compressioirbeloyvbaround 16 foot perY 4 nfcom'pression.

` asishown'fand describedy f .p Fa thicknessfoff aifi-ncn'ioiexamplecthenitlieifcompression re-1@kl sistance will be substantially lessened over the whole range of compression activity. Also, instead of compression relief starting to become eiective at piston velocities around .6 foot per second,'these thinner disks willstart to-become effective at substantially lesser piston velocities and by using still thinner disks it is possible to initiate compression relief at all piston velocities if such be desired although at extreme conditions of thinning the disks'in relation to relatively high rebound pressures I have noticed some tendency for rebound pressures to dish the disks in the annular groove 53 and give rise to resistance losses on rebound and compression as an incident to disk deformations. A typical performance characteristic of my shock absorber employing the aforesaid .O06 relief valving disks is indicated at 2 I0 in Fig. 15. Of course when such valving is'employed thenthe table of per cent resistance reductions is no longer correct as these values-Will be differentand can be readily computed from curve 208. Generally speaking these 1 percentages will be substantially greater and will be initially effective at a substantially lower piston velocity. Conversely by making these relief disks thicker, for example about .012 of an inch, compression relief in my illustrated shock absorber becomes eective at around 1.3 feet per second piston velocityV and compression resistance values are substantially greater than as indicated for` curve 2|0 in Fig. 15. Compression resistances for such .012 disks are of the order of -.the curve 2|!!b in Fig. l5; Compression performance characteristics between the illustrated curves 2li), 2| and 2li)b may obviously be readily obtained as desired by appropriate selection in the thickness of the relief disks employed or in the number of such disks. It will be apparent that with the .006 compression relief disks the corresponding compression curves of Fig. 13 will peak at substantially lesser maximum values than as indicated for the curves |89, |92, and |93 with more pronounced deviation as the maximum piston velocities increase. correspondingly with the .012 disks the compression curves will peak at substantially greater maximum values than as indicated for the curves |89, |92, and |93 likewise with more pronounced deviation as the maximum piston velocities increase.

I claim: y

In a direct acting hydraulic shock absorber of the type having a working cylinder closed at one end through which a piston rod extends for operable connection with a working piston reciprocably mounted in said cylinder to provide a rebound chamber adjacent said closed cylinder end and a compression chamber adjacent the other cylinder end, a tubular member surrounding said cylinder toprovide a liquid reservoir, and check valve means between said compression chamber and said reservoir having a relatively large unrestricted liquid iiow capacity sufcient to accommodate free liquid flow from said reservoir to said compression chamber during the rebound stroke of said piston towards said closed cylinder end but preventing return passage of liquid from said compression chamber to said reservoir during the compression stroke of said piston towards said check valve means; the face of the piston which bounds the rebound chamber being provided with liquid conducting groove means defining a seat portion, said groove means having relatively unrestricted constantly open communication with said compression chamber through passages formed in said piston, annular disk valve means carried with said piston and having the innerv peripheral portion thereof iixed axially relative to said piston'and provided with an outer peripheral portion overlying said groove means and having a seat potion normally engaged with said piston seat portion, the first mentioned said piston seat portion being notched to provide, in cooperation with said overlying portion of said disk valve means, constantly open two-Way liquid flow restricting shuttle passage means having one end thereof constantly open directly to the rebound chamber and having the other end thereof constantly open to the compression chamber through said groove means and said piston'passages, said notched shuttle passage means being operative to restrict liquid interow between said chambers on both the compression and rebound strokes of the piston to thereby cause the piston to perform useful resistance work on both strokes of the piston, said notched shuttle passage means having a liquid iiow capacity sufcient to substantially fill said rebound chamber on all compression strokes of the piston and said annulus disk valve member operating during piston compression strokes and in response to predetermined pressure differential between said chambers to allow liquid fiow from said piston passages and groove means thence between said disk valve member and said piston seat portion to the rebound chamber, liquid ow restricting escape passage means operative to restrict liquid flow from the compression chamber to the reservoir, said notched shuttle passage means having such liquid flow restricting capacity relative to the liquid flow restricting capacity of said escape passage means that only a minor portion of the compression resistance rwork during the compression stroke of the piston is effected by the flow resistance offered by said liquid escape passage means and the major portion of the compression resistance work is effected by the flow resistance offered by said notched shuttle passage means, all of the liquid displaced from said rebound chamber by all rebound strokes of the piston being passed only to said compression chamber and passing through said notched shuttle passage means and all of the liquid flowing to the rebound chamber during all compression strokes of the piston being passed only from said compression chamber through said groove means and through said notched shuttle passage means and through the space between said disk valve member and said piston seat portion by flexing of the outer peripheral portion of said disk valve member away from said piston seat portion.

DONALD T. BALL.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date Re. 23,421 Whisler Oct. 16, 1951 2,087,451 Rossman et al July 20, 1937 2,107,974 Becher-eau et al. Feb. 8, 1938 2,335,907 Boor et al. Dec. 7, 1943 2,432,937 Rossman Dec. 16, 1947 2,497,972 Beecher Feb. 2l, 1950 2,546,038 McIntyre et al. Mar. 20, 1951 2,551,749 Lewton May 8, 1951 

